Gravity wave propagation directions inferred from satellite observations including smearing effects

We simulate space-based, sublimb viewing observations of airglow brightness fluctuations caused by atmospheric gravity wave interactions with the O-2 atmospheric airglow, and we demonstrate that because of the geometry associ ated with such observations, the brightness fluctuations observed for the o ptically thick 0-0 band emission will always appear stronger for waves trav eling toward the observer (the satellite). The effect should be most notice able for waves having relatively small vertical wavelengths (similar to 10 km) and horizontal wavelengths of 50 km or greater. For waves of short (sim ilar to 100 km) horizontal wavelength, the brightness fluctuation anisotrop y with respect to viewing direction may also be evident in the optically th in 0-1 band emission. We demonstrate that the waves will be observable desp ite the fact that an instrument requires a certain finite integration time to achieve a desired signal-to-noise ratio. Therefore the 180 degrees ambig uity in wave propagation direction associated with space-based observations may be eliminated for waves of small vertical wavelength that are dissipat ing in the upper mesosphere and lower thermosphere. It is these same waves that may be expected to be important to the energy and momentum budgets of the mesosphere/lower thermosphere region.